Universal gripper for tote and sub-tote transport

ABSTRACT

A universal gripper is disclosed for transferring totes and sub-totes, for example in an order fulfillment center. The universal gripper includes adjustable tines and pins capable of being positioned to engage within slots in the different configurations of totes and sub-totes.

PRIORITY CLAIM

The present application claims priority to U.S. Provisional Patent Application No. 62/542,551, filed on Aug. 8, 2017, entitled “UNIVERSAL GRIPPER FOR TOTE AND SUB-TOTE TRANSPORT,” which application is incorporated by reference herein in its entirety.

BACKGROUND

An order-fulfillment system for use in supply chains, for example in retail supply chains, may fulfill orders for individual goods or product units, also referred to herein as “eaches.” Such eaches are transported within a facility such as a distribution center or retail store within containers, referred to herein as totes. Such totes may include smaller containers, referred to herein as sub-totes, to allow different goods to be stored and transported together within a tote. A system is needed for the efficient transfer of totes, and the transfer of sub-totes between totes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C show Sub-tote and tote configurations.

FIG. 2 shows a top view of universal gripper.

FIG. 3 shows a front view of universal gripper.

FIG. 4 shows an end view of universal gripper.

FIGS. 5A-5G show top view of sub-totes and corresponding universal grippers.

FIGS. 6-9 show views of a sub-tote engagement by the universal gripper.

FIGS. 10-12 show full tote engagement by the universal gripper.

FIG. 13 is a top view of the universal gripper mounted on Cartesian robot.

FIG. 14 is a front view of the universal gripper mounted on Cartesian robot.

FIGS. 15-25 illustrate transfer of a sub-tote between full totes using a Cartesian robot.

FIG. 26 shows a universal gripper mounted to six-axis robot.

FIGS. 27 and 28 show a universal gripper operating within a workstation for transferring sub-totes between totes.

DETAILED DESCRIPTION

Embodiments of the present technology will now be described with reference to the figures, which in general relate to a universal gripper for transferring totes and sub-totes, for example in an order fulfillment center. The universal gripper includes adjustable pins and tines capable of being positioned to engage within slots in the different configurations of totes and sub-totes. The tines include tabs, referred to herein as lifting tabs. Once the lifting tabs on the tines pass through the slots on the sub-totes, the tines are translated apart so that the lifting tabs lock the sub-tote on the tines. The universal gripper may thereafter transport the tote or sub-tote to a new position secured on the universal gripper.

It is understood that the present invention may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the invention to those skilled in the art. Indeed, the invention is intended to cover alternatives, modifications and equivalents of these embodiments, which are included within the scope and spirit of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be clear to those of ordinary skill in the art that the present invention may be practiced without such specific details.

The terms “top” and “bottom,” “upper” and “lower” and “vertical” and “horizontal” as may be used herein are by way of example and illustrative purposes only, and are not meant to limit the description of the invention inasmuch as the referenced item can be exchanged in position and orientation. Also, as used herein, the terms “substantially” and/or “about” mean that the specified dimension or parameter may be varied within an acceptable manufacturing tolerance for a given application. In one embodiment, the acceptable manufacturing tolerance is ±0.25%.

FIGS. 1A-1C illustrate totes 100 including different configurations of sub-totes 102. FIG. 1A shows an example of six small sub-totes 102 a filling the available area of tote 100. FIG. 1B shows an example of three medium sized sub-totes 102 b filling the available area of tote 100. FIG. 1C shows an example of two large sub-totes 102 c filling the available area of tote 100. Totes 102 a are referred to herein as one-sixth sub-totes 102 a, totes 102 b are referred to herein as one-third sub-totes 102 b and totes 102 c are referred to herein as one-half sub-totes 102 c. There may be other configurations of sub-totes 102 within tote 100, such as for example one-eighth sub-totes comprising eight sub-totes which fill the available area of tote 100. The tote 100 may further be used with no sub-totes 102.

The universal gripper of the present technology is able to manipulate (including to grip and transfer) the sub-totes 102 of any configuration, as well as the tote 100 as a whole. As explained below, the universal gripper includes tines which engage within slots 120 provided in the perimeter of tote 100 and different configurations of sub-totes 102. This minimizes the structure within the tote 100 and sub-totes 102 needed for operation with the universal gripper, and maximizes the space within the tote 100 and sub-totes 102 available for stored goods.

FIGS. 2, 3 and 4 are top, side and end views, respectively of a universal gripper 110 according to an embodiment of the present technology including projecting pieces in the form of tines 112 for engaging within slots in the tote 100 or sub-totes 102. The tines 112 extend down (along z-axis) into the space between an outer wall of the sub-totes 102 and an inner wall of the full tote 100. In particular, the sidewalls of the tote 100 are provided with a draft angle so that the tote sidewalls slant outward slightly from a bottom to a top of the sidewalls. The draft angle of the sidewalls in tote 100 provide space for receiving the tines 112, while allowing the bottom footprint of the sub-totes 102 to approximate the bottom footprint of the full tote 100.

The tines 112 are mounted on a frame 114. In particular, a first side of the frame includes first and second tines 112 driven to move along the first side of the frame (along the x-axis) by first and second motors 116 (one such motor labeled in FIG. 4). Each of the motors 116 may for example be a servomotor. In one example, the each of the first and second tines 112 on the first side of frame 114 may be attached to a ball slide and driven by parallel leadscrews 122 (FIG. 6) by the motors 116. The translating tines 112 in the first side of frame 114 may alternatively be driven with toothed time belts. A second side of the frame 114, opposed to the first side, may include a second pair of tines, also driven to move along the second side by a pair of motors 116 as described above for the first side of frame 114.

A processor (not shown) controls the motors 116 to drive the translating tines 112 along the sides of the frame 114 to appropriately space apart the translating tines 112 to grip the tote 100 and sub-totes 102 for any sub-tote configuration. In particular, the tines may be driven to a position so as to align with the slots in the outer walls of the tote 100 and the slots in the outer walls of the sub-totes 102 of any sub-tote configuration. Also, as explained below, the translating tines in each side may be driven to shift once positioned within the slots of a sub-tote to engage the sub-tote for lifting.

In embodiments, the tines 112 remain a fixed distance from each other along the y-axis. However, it is conceivable that the tines 112 on opposed sides of the frame 114 move toward or away from each other in further embodiments. The gripper 110 includes a hub 118 which mounts to a shaft 158 (shown in FIG. 15) capable of translating the gripper 110 and rotating the gripper 110 at least 180° about an axis through the shaft and hub 118.

FIGS. 5A-5F are top views showing the positioning of the tines 112 for gripping the respective configurations of sub-totes 102. FIG. 5G shows the positioning of the tines 112 for gripping the tote 100. In particular, FIG. 5A shows a tote 100 filled with one-sixth sub-totes 102 a. FIG. 5B shows the orientation of the gripper 110 and tines 112 for removing a one-sixth sub-tote 102 a from the tote 100 shown in FIG. 5A. Owing to the small size of the one-sixth sub-totes 102 a, the tines 112 engage a single side of a sub-tote 102 a for transport of the sub-tote 102 a. The sub-tote 102 a shown in FIG. 5B is gripped by a pair of tines 112 on one edge (bottom edge in FIG. 5B) of the frame 114. If the sub-tote 102 a were instead seated within the tote 100 in the other position along the y-axis, the sub-tote 102 a would be gripped by a pair of tines 112 on the opposite edge (top edge in FIG. 5B) of the frame 114.

FIG. 5C shows a tote 100 filled with one-third sub-totes 102 b. FIG. 5D shows the orientation of the gripper 110 and tines 112 for removing a one-third sub-tote 102 b from the tote 100 shown in FIG. 5C. As the sub-tote 102 b spans the entire width of the tote 100 along the y-axis, the sub-tote 102 b may be gripped by a first pair of tines 112 along a first edge of frame 114, by a second pair of tines 112 along a second edge of frame 114 opposed to the first edge, or by both pairs of tines 112 along the two opposed edges.

FIG. 5E shows a tote 100 filled with one-half sub-totes 102 c. FIG. 5F shows the orientation of the gripper 110 and tines 112 for removing a one-half sub-tote 102 c from the tote 100 shown in FIG. 5E. The sub-tote 102 c shown in FIG. 5F is gripped by a pair of tines 112 on one edge (bottom edge in FIG. 5F) of the frame 114. If the sub-tote 102 c were instead seated within the tote 100 in the other position along the y-axis, the sub-tote 102 c would be gripped by a pair of tines 112 on the opposite edge (top edge in FIG. 5F) of the frame 114.

FIG. 5G shows the orientation of the gripper 110 and tines 112 for gripping and transporting a full tote 100 (which could have any number and type of sub-totes within the tote 100, including no sub-totes).

As shown in FIGS. 5A-G, the design of the universal gripper 110 allows gripping and transport of all sub-tote combinations using the same tines 112 and motors 116 on the frame 114. In applications where only sub-totes, or full totes are handled with the gripper, only those motors may be populated on the frame to minimize cost.

FIGS. 6-9 illustrate an example of the universal gripper 110 acquiring and transporting a sub-tote 102 a. As shown, the sidewalls of sub-tote 102 a include slots 120 provided in a horizontal flange in a top portion of the sidewalls. The bottom ends of tines 112 (opposite the ends affixed to the frame 114) have tapered ends in both width and thickness to promote reliable engagement in the tote/sub-tote slots 120.

As shown in FIG. 6, the motor 116 on one side of the gripper 110 moves the translating tines 112 along the x-axis so that the translating tines 112 on one side of the gripper 110 align with the slots 120 of the sub-tote 102 a. The tines 112 may be aligned with the slots 120 based on the known spacing of the slots 120 on sub-tote 102 a and the known position of the gripper 110 with respect to the sub-tote 102 a. Alternatively or additionally, the gripper 110 may include optical sensors capable of aligning the translating tines with the slots 120.

Once aligned with the slots 120, the tines 112 are lowered along the z-axis so that ends of the tines engage within the slots 120 as shown in FIG. 7. The entire gripper may move vertically along the z-axis to position the tines 112 within the slots 120. Alternatively, the tines may be mounted for vertical translation on the gripper 110 and lower relative to the frame 114 into the slots 120.

The tines 112 lower through the slots 120 until lifting tabs 128 on respective tines pass through the slots 120, as shown in FIG. 7. Thereafter, as shown in FIG. 8, the tines are moved away from each other along the x-axis so that the lifting tabs 128 extend underneath the top external flange of the sub-tote (in the direction of the arrows in FIG. 8). In this position, the lifting tabs 128 prevent removal of the tines 112 from the slots 120. The tines provide constraints against the sides of the sub-tote 102 a that allow it to be lifted by the one side only (the tines prevent the sub-tote from rotating along the x-axis as viewed in the FIGS. 8 and 9). Thereafter, the universal gripper 110 may move the sub-tote 102 a with the sub-tote 102 a locked on the gripper. The lifting tabs 128 bear the lifting weight as the gripper 110 and sub-tote 102 a are lifted. Supported on the lifting tabs 128, the weight of the sub-tote and its contents bias the sub-tote to rotate about the x-axis, against the tines 112, thus preventing wobbling of the sub-tote as it is transferred. To release the sub-tote 102 a, the translating tines are moved toward each other until the lifting tabs 128 move clear of the top external flange. Thereafter, the tines 112 may be moved upward out of the slots 120.

It is understood that the other sub-totes 102 b and 102 c may be gripped and transported in the same manner as described above for sub-tote 102 a. Tines 112 may engage within slots 120 on a single side of the sub-totes. Alternatively, where a sub-tote extends the full width of the tote along the y-axis (such as for example sub-tote 102 b) the tines 112 may engage within slots 120 on opposed sides of the tote or sub-totes.

FIGS. 10-12 show engagement of the universal gripper 110 with a full tote 100. In this embodiment, the vertically extending tines 112 may be omitted from the gripper 110. The gripper 110 may instead include projecting pieces in the form of horizontally extending pins 132 (seen partially in FIG. 12; recessed within the frame 114 in FIGS. 10 and 11), two on each of the long sides of the gripper 110. The horizontal pins 132 are capable of extending along the y-axis by motors 136 mounted on the frame 114. Each pair of pins 132 on opposed sides of frame 114 may be driven by a single motor 136.

FIG. 11 shows the gripper 110 fully inserted into the full tote 100, with the horizontal pins 132 still retracted within the frame 114. Chamfered lead-ins 138 (FIG. 10) are provide on the ends of the frame 114, orthogonal to the horizontal pins 132 to promote reliable positioning. FIG. 12 shows the horizontal pins 132 extended outward and into slots 140 in the top perimeter rim of the tote 100. There may be two slots 140 on each long side of the tote 100 in this configuration. The pins 132 may have bulleted ends to promote reliable engagement into the tote rim. The pins 132 may further have shoulders that abut just inside the rim to prevent the tote from shifting on the tines during lifting or manipulation of the tote.

FIGS. 10-12 show a pair of pins 132 engaging within a pair of slots 140 on one side of the tote 100. A second pair of pins 132 may engage within a second pair of slots 140 on the opposed side of tote 100 as well to provide four engagement points of gripper 110 with the tote 100. With the pins 132 secured within slots 140, the gripper 110 may lift and transport the tote 100. To release the tote 100, the motors 136 may retract the horizontal pins 132 from the slots 140.

FIGS. 13 to 25 illustrate a universal gripper 110 mounted to a Cartesian robot 150. The robot 150 is driven along a pair of rails 152 by a pair of motors 154 (FIG. 15) on the robot 150. For example, each rail 152 may include toothed timing belt drives, driven by one through-shaft servo motor 154. The through shaft is attached to the two parallel drives to ensure the two sides are driven uniformly.

The robot 150 further includes a shaft 158 which affixes within hub 118 of the gripper 110 to translate and/or rotate the gripper 110. FIG. 13 is a top view of the robot 150 and gripper 110 over a number of totes 100. FIG. 14 is a side view of the robot 150 and gripper 110 over a number of totes 100. And FIGS. 15-25 are perspective views of the robot 150 and gripper 110 transferring a sub-tote 102 from one tote to another tote. The Cartesian robot and gripper may be mounted within the storage racking to enable in-storage transfers of sub-totes between the full totes. This is used to defragment the storage; i.e. combine empty sub-totes together in full totes, and thereby increase storage density within the system.

FIG. 15 shows the gripper 110 in a fully raised position. Depending on tine length, gripper does not need to be raised to full height position when not carrying a sub-tote. FIG. 16 shows the gripper 110 lowering its tines into slots in top exterior flange of a one-sixth sub-tote 102 a. FIG. 17 shows the first pair of gripper tines 112 fully inserted into sub-tote slots, with the tines in sub-tote driven apart to position lifting tabs underneath the slots.

The figures also show a second one-sixth sub-tote 102 a in the position next to (or opposite) the sub-tote 102 a to be transferred. The second pair of gripper tines on the opposite side penetrate through the slots in the top exterior flanges of this opposite side sub-tot. However, the second pair of tines are not driven apart thereby allowing the second pair of tines to be lifted without lifting the opposite side sub-tote. If the one-sixth, or one-half sub-totes on opposite sides of the full tote are desired to be lifted together, then all tines are driven apart to position the lifting tabs underneath the top exterior flanges of both sub-totes.

FIG. 18 shows the sub-tote 102 a in the half-lifted position out of the source tote 100, supported on the first pair of tines 112. FIG. 19 shows the sub-tote 102 a fully lifted out of the source tote 100. FIG. 20 shows the Cartesian robot 150 translating and rotating the gripper 110 and sub-tote 102 a simultaneously. Rotation of the sub-tote 102 a is needed in this example, as the sub-tote 102 a is being placed in the opposite side of the destination tote, as compared to the source tote. FIG. 21 shows continued rotation and translation of the sub-tote 102 a on the gripper 110 and robot 150. If the sub-tote 102 a was to be positioned in the middle of the other side, or opposite corner of the source corner location, the tines would also be translated within the gripper 110 during the movement of the gripper.

FIG. 22 shows the Cartesian robot 150 having translated and rotated the sub-tote 102 a over its destination position. FIG. 23 shows the Cartesian robot having partially lowered the gripper 110 and sub-tote 102 a into the destination location. FIG. 24 shows the Cartesian robot having fully lowered the gripper and sub-tote into the destination location. Once in this position, the tines 112 are moved toward each other to disengage the lifting tabs from underneath the top external flange of the sub-tote. The tines on the opposite side of the gripper are positioned to allow them to extend into the slots of other sub-totes already contained within the destination full tote. As an alternative, the gripper 110 could be lengthened to permit the tines not lifting or lowering sub-totes to straddle the outside of the full tote. FIG. 25 shows the gripper 110 and robot 150 after releasing the sub-tote 102 a in its destination position. The gripper 110 with its tines 112 are lifted out of the slot of the sub-tote 102 a.

FIG. 26 shows an alternative embodiment where the universal gripper 110 is mounted to a six-axis robot 160, which can be used to transport full totes 100 and/or sub-totes 102. This configuration may be used in distribution centers and workstations where full totes containing sub-totes are presented together.

FIGS. 27 and 28 are perspective and side views of a universal gripper 110 mounted above dynamic workstation 170. Mobile robots 174 climb through a workstation 170 and present totes 100 with sub-totes 102 to the Cartesian robot 150 with a universal gripper 110. This can be used for defragmenting empty sub-totes within the system, or transferring sub-totes into totes for store replenishment. An example of a dynamic workstation 170 is shown for example in U.S. patent application Ser. No. 15/591,956, entitled, “Order Fulfillment System,” filed May 10, 2017, and U.S. patent application Ser. No. 15/956,346, entitled, “Picking Workstation with Mobile Robots & Machine Vision Verification of Each Transfers Performed by Human Operators,” filed Apr. 18, 2018, which applications are incorporated herein by reference in their entirety.

The foregoing detailed description has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the description to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. The described embodiments were chosen in order to best explain the principles of the claimed system and its practical application to thereby enable others skilled in the art to best utilize the claimed system in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the method be defined by the claims appended hereto. 

We claim:
 1. A universal gripper for transporting at least one of a tote and a sub-tote, comprising: a frame; a pair of projecting pieces, at least one of which is translationally mounted along one side of the frame, wherein the projecting pieces comprise pins that are oriented parallel to the frame and configured to move in a plane parallel to the frame to engage within slots formed in the at least one of a tote and sub-tote; a drive mechanism configured to position the pair of projecting pieces so as to align with a pair of slots on one of the at least one of a tote and sub-tote; wherein engagement of the pair of projecting pieces within the at least one of a tote or sub-tote supports the at least one of a tote or sub-tote on the gripper for transport.
 2. The universal gripper of claim 1, wherein the universal gripper is configured to be mounted to a Cartesian robot for translating and rotating the universal gripper.
 3. The universal gripper of claim 1, wherein the universal gripper is configured to be mounted to a six-axis robot for translating and rotating the universal gripper.
 4. The universal gripper of claim 1, wherein the universal gripper is configured to operate at a workstation for transferring sub-totes between totes.
 5. The universal gripper of claim 1, wherein the pins comprise four pins configured to fit in four slots in the at least one of the tote and sub-totes.
 6. A universal gripper for transporting a sub-tote to or from a tote in a reference coordinate system comprising x, y and z orthogonal axes, the universal gripper comprising: a pair of tines mounted on the universal gripper with a spacing that is configured to vary along the x-axis, the pair of tines each including a length extending along the z axis; a lifting tab on at least one of the pair of tines, the lifting tab extending away from the length of the tine; a drive mechanism configured to move one or both tines of the pair of tines along the x-axis; wherein the universal gripper is configured to secure the sub-tote on the universal gripper by locking the pair of tines within a pair of slots of the sub-tote by the lifting tab; and wherein the pair of tines are configured to move along the z-axis into a space between an outer wall of the sub-tote and an inner wall of the tote.
 7. The universal gripper of claim 6, wherein the universal gripper is configured to secure the sub-tote on the universal gripper by positioning the pair of tines along the x-axis by the drive mechanism into alignment with the pair of slots in the sub-tote, moving the pair of tines along the z-axis to position the pair of tines within the pair of slots with the lifting tab passing through a slot of the pair of slots, and moving the pair of tines along the x-axis by the drive mechanism to lock the lifting tab within the slot.
 8. The universal gripper of claim 6, the universal gripper further comprising a frame oriented in a plane comprising the x and y axes, wherein the pair of tines are translationally mounted on a side of the frame and configured to move along the x-axis by the drive mechanism to work with sub-totes of different sizes having pairs of slots spaced different distances from each other.
 9. The universal gripper of claim 6, further comprising a processor for controlling a spacing of the pair of tines with respect to each other along the x-axis.
 10. The universal gripper of claim 6, further comprising a hub on which the frame is mounted, wherein the hub configured to rotate the frame, and a sub-tote secured on the universal gripper.
 11. A system comprising a universal gripper mounted to a robot for transporting a sub-tote in a reference coordinate system comprising x, y and z orthogonal axes between first and second totes, the sub-totes being an array of different sizes fitting within the first and second totes and each sub-tote including one or more slots having first and second ends, a spacing between the first and second ends of the slots varying depending on a size of the sub-tote in the array of different sized sub-totes, the system comprising: a pair of tines mounted on the universal gripper with a spacing that is configured to vary along the x-axis, the pair of tines each including a length extending along the z axis; a lifting tab on at least one of the pair of tines, the lifting tab extending away from the length of the tine; and a drive mechanism on the universal gripper configured to move one or both tines of the pair of tines along the x-axis, the drive mechanism configured to vary a spacing between the tines to fit within the one or more slots of each sub-tote in the array of different sized sub-totes, depending on the spacing between the first and second ends of the one or more slots of a particular sized sub-tote being transported, and the drive mechanism configured to move one or both tines of the pair of tines toward or away from each other after the tines are positioned in the one or more slots to lock the pair of tines within the one or more slots by the lifting tabs; wherein the robot is configured to move the sub-tote, secured on the universal gripper from the first tote to the second tote.
 12. The system of claim 11, further comprising a second drive mechanism on the robot configured to move the universal gripper along the z-axis; wherein universal gripper and robot are configured to secure the sub-tote on the universal gripper by positioning the pair of tines along the x-axis by the first drive mechanism into alignment with the pair of slots in the sub-tote, moving the pair of tines along the z-axis by the at least second drive mechanism to position the pair of tines within the pair of slots with the lifting tab passing through a slot of the pair of slots, and moving the pair of tines along the x-axis by the first drive mechanism to lock the lifting tab within the slot.
 13. The system of claim 11, the universal gripper further comprising a frame oriented in a plane comprising the x and y axes, wherein the pair of tines are translationally mounted on a side of the frame and configured to move along the x-axis by the first drive mechanism.
 14. The system of claim 11, further comprising a processor for controlling the first drive mechanism.
 15. The system of claim 11, wherein the robot is a six-axis robot configured to translate and rotate the universal gripper.
 16. The system of claim 15, wherein the six-axis robot is configured to transport the sub-tote from any position within the first tote to any position in the second tote.
 17. The system of claim 15, wherein the six-axis robot is configured to rotate the sub-tote from any orientation about the z-axis in the first tote to any orientation about the z-axis in the second tote.
 18. The system of claim 11, wherein the robot is a Cartesian robot configured to translate the universal gripper.
 19. The system of claim 18, further comprising a hub on the universal gripper for rotating the sub-tote about the z-axis as it is transferred between the first and second totes.
 20. The system of claim 11, wherein the tines support the sub-tote on a single side of the sub-tote.
 21. The system of claim 11, wherein the tines are mounted on a single side of the frame and configured to move toward and away from each other along the side of the frame.
 22. A method for transporting a sub-tote in a reference coordinate system, the method comprising: (a) moving a pair of tines in along a first axis to positions aligned with a pair of slots of the sub-tote; (b) moving the pair of tines along a second axis, orthogonal to the first, through the slots, such that a lifting tab on at least one of the tines passes through at least one of the slots; (c) moving the pair of tines along the first axis such that the at least one lifting tab is misaligned with, and prevented from passing through, the one or more slots to secure the sub-totes on at least one of the tines; and (d) transporting the sub-tote once secured on at least one of the tines, wherein the sub-tote is empty and said step (d) comprises a decanting step to move the empty sub-tote from a first tote to a second tote to free up space in the first tote.
 23. The method of claim 22, wherein said step (d) further comprises linearly translating the sub-tote.
 24. The method of claim 22, wherein said step (d) further comprises rotating the sub-tote. 